1. Field of the Invention
The present invention relates to a magnetoresistance effect element which can be used for a magnetic reproducing head or a magnetic sensor.
2. Description of the Background Art
A magnetoresistance effect element is adapted to detect a change in the electrical resistance of a magnetic film caused by the application of a magnetic field, thereby measuring the field strength and its change. In general, therefore, the magnetoresistance effect element must have a high magnetoresistance ratio and a small operating field strength at room temperature. A magnetic material for such a magnetoresistance effect element is generally prepared from an Fe-Ni alloy (Permalloy). Due to an extremely small magnetoresistance ratio of 2 to 3%, however, the Fe-Ni alloy is not preferable as the magnetic material for the magnetoresistance effect element, although the same has a small operating field strength of about 10 Oe.
A novel magnetoresistance effect film is disclosed in "Physical Review Letters" Vol. 68, No. 25, 22 Jun. 1992, pp. 3745-3748. This magnetoresistance effect film is formed by a CoCu alloy film consisting of Co and Cu which is in a eutectic relation of being atomically mixed with Co in a liquid phase but not in a solid phase. This alloy film exhibits a high magnetoresistance ratio exceeding 10% at an ultralow temperature of 10K. At room temperature, however, this alloy film has a small magnetoresistance ratio of 6 to 7% while its operating field strength is extremely increased to about 6000 Oe.
The inventors have proposed a magnetoresistance effect material consisting of atoms of a ferromagnetic metal and atoms of a non-magnetic metal, which is in a non-soluble relation of not being atomically mixed with the ferromagnetic metal in solid and liquid phases, as a magnetoresistance effect material having a higher magnetoresistance ratio (U.S. Ser. No. 08/216,185).